Search-and-rescue operations are underway for two US Marine Corps aircraft involved in a “mishap” 200 miles off the coast of Japan.

An F/A-18 fighter and a KC-130 cargo plane taking part in a aerial refueling exercise collided and crashed, the US military said.

Two crew members were rescued, but one has since died and the other five are still missing.

Search-and-rescue operations are underway for two US Marine Corps aircraft involved in a “mishap” 200 miles off the coast of Japan, the Marine Corps said Wednesday.

The planes in question were an F/A-18 Hornet fighter and a KC-130 Hercules cargo plane that were taking part in aerial refueling exercise.

The KC-130 had five crew aboard and the F-18 two, according to the Marine Corps. Five crew members are still missing.

“The aircraft involved in the mishap had launched from Marine Corps Air Station Iwakuni and were conducting regularly scheduled training when the mishap occurred,” the service said in a statement published by USNI News.

The incident happened around 2 a.m. local time on December 6. Japanese search-and-rescue aircraft responded immediately, the Corps said, adding that the circumstances were under investigation.

One of the seven missing was rescued alive, a spokeswomen for the 1st Marine Aircraft Wing said Wednesday evening. A second crew member was found alive around 60 miles from Shikoku island, according to the Associated Press, citing Japanese officials.

“The search and rescue operations continue for the remaining five US Marines,” the III MEF Marines wrote in a Facebook update.

As of Thursday morning, on of the two rescued crew members was in fair condition. The other, located 10 hours after the crash and taken aboard a Japanese military vessel, has died.

The search – conducted by the US 7th Fleet, a Navy P-8A Maritime Patrol reconnaissance Aircraft flying out of Kadena Air Force Base, the Japan Maritime Self-Defense Force, and the Japanese Coast Guard – is ongoing in an area about 200 miles of the Japanese coast, the Marine’s post said.

Katsutoshi Kawano, chief of the Japanese Self-Defence Forces’ Joint Staff, told Reuters on Wednesday: “We plan to keep at it all through the night.”